Investigations on the gas-stabilized micro-spark method in different gas atmospheres used for the emission analysis of steel samples

Abstract Different gas atmospheres (air, nitrogen, carbon dioxide, argon) were investigated for stabilizing the micro-spark discharge for steel sample analyses. The influences of the gas flow rate on absolute and relative (log) line intensities ( Y and Δ Y ) have been studied; the optimum lies between 70 and 120 dm 3 h −1 . Sparking-off curves, and radial and axial intensity studies demonstrated the effects of different counter-electrodes associated with different protecting gases. Argon gas with graphite or carbon counter-electrodes resulted in a larger plasma volume and the spectral excitation was uniform over the length of the spark gap. Statistical tests of analytical curves and analysis results confirmed that the argon-stabilized micro-spark method with graphite or carbon counter-electrodes yields results with a higher precision and accuracy than the traditional system. The total relative error of the analytic results is less than 5% for Cr, Mn, Si, Mo and Cu, at most 7–8% for Ni, and 7–12% for Ti.